Department of Internal Medicine 1, Laboratory of Molecular Gastroenterology & Hepatology, UKSH-Campus Kiel, Arnold-Heller-Strasse 3, Bldg. 6, 24105 Kiel, Germany.
Int J Oncol. 2011 Jan;38(1):257-66.
Members of the Slug/Snail family of transcription factors are thought to drive epithelial-mesenchymal-transition (EMT) in preneoplastic epithelial cells, thereby contributing to malignant transformation. One mediator in the EMT of pancreatic ductal adenocarcinoma (PDAC) cells and a potential target gene of Slug is the cellular adhesion molecule L1CAM. Using the human pancreatic ductal epithelial cell line H6c7 and the PDAC cell line Panc1, we could show that along with TGF-β1-induced EMT, L1CAM expression is increased in a Slug- but not Snail-dependent fashion. Two E-box recognition motifs in the L1CAM promoter upstream of the most distal transcriptional start site could be verified by gel shift and supershift assay to interact with Slug. ChIP assays detected an increased interaction of Slug with both recognition motifs of the human L1CAM promoter in TGF-β1-treated H6c7 cells, whereas binding of Snail was downregulated. Moreover, ChIP assays with Panc1 cells confirmed this interaction of Slug with the human L1CAM promoter and further detected an interaction of both recognition sites with RNA-polymerase II in a Slug-dependent fashion. Luciferase reporter gene assays using wild-type or single- and double-mutated variants of the L1CAM promoter confirmed transcriptional activation by Slug involving both recognition motifs. By demonstrating the direct transcriptional control of L1CAM expression through Slug during TGF-β1-induced EMT of PDAC cells, our findings point to a novel mechanism by which Slug contributes quite early to tumorigenesis. Moreover, our study is the first one describing the control of the human L1CAM promoter in tumor cells.
Slug/Snail 转录因子家族成员被认为在癌前上皮细胞中驱动上皮-间充质转化(EMT),从而促进恶性转化。在胰腺导管腺癌(PDAC)细胞的 EMT 中是一种介质,也是 Slug 的潜在靶基因,是细胞黏附分子 L1CAM。我们使用人胰腺导管上皮细胞系 H6c7 和 PDAC 细胞系 Panc1,证明随着 TGF-β1 诱导的 EMT,L1CAM 表达增加,这是 Slug 而非 Snail 依赖性的。在最远端转录起始位点上游的 L1CAM 启动子中,两个 E 盒识别基序可以通过凝胶迁移和超迁移测定来验证与 Slug 相互作用。ChIP 测定检测到 TGF-β1 处理的 H6c7 细胞中 Slug 与人类 L1CAM 启动子的两个识别基序的相互作用增加,而 Snail 的结合则下调。此外,用 Panc1 细胞进行的 ChIP 测定证实了 Slug 与人类 L1CAM 启动子的这种相互作用,并进一步检测到 Slug 依赖性的两个识别位点与 RNA 聚合酶 II 的相互作用。使用野生型或 L1CAM 启动子的单突变和双突变变体的荧光素酶报告基因测定证实了 Slug 通过两个识别基序对 L1CAM 表达的直接转录激活。通过证明 Slug 在 TGF-β1 诱导的 PDAC 细胞 EMT 过程中直接转录调控 L1CAM 表达,我们的发现指出了 Slug 早期促进肿瘤发生的新机制。此外,我们的研究是第一个描述肿瘤细胞中人类 L1CAM 启动子控制的研究。